Sprinkler pre action system 1

[remp]

Is a sprinkler action system where

1) The preaction valve opens and the the pipe fill with water only when a smoke head is activated and a sprinkler head breaks (detected thro' loss of compressed air pressure)
or
2) the pre action valve open and the pie fill with water when a smoke head is activate only

2) If 2 is the answer does this mean I have to drain the system everytime there is a false alarm?

is it 1 or 2....???

 

[DRWeig]

It's 2.

Get used to draining it.

Good on ya,

Goober Dave

 

[imok2]

Two separate events must happen to initiate sprinkler discharge. First, the detection system must identify a developing fire and then open the preaction valve. This allows water to flow into system piping, which effectively creates a wet pipe sprinkler system. Second, individual sprinkler heads must release to permit water flow onto the fire.

 

[KiwiMace]

There are two types of preaction system - Single Interlock and Double Interlock.

Single interlock floods the pipe when the smoke detector alarms. This is the one that you have to drain and dry the pipework out before rearming.

Double interlock requires both the alarm and a broken head before the valve opens.

 

[DRWeig]

Kiwi,

Does the double interlock require compressed air and a pressure switch, or other means of sensing sprinkler head open?

Good on ya,

Goober Dave

 

[remp]

compresse air or nitrogen to keep the water back after the per action valve opens when a smoke head goes off. A pressure switch will trigger an alarm if there is a leak due to broken head

 

[KiwiMace]

Yes, both systems use compressed air (or less often Nitrogen). A small vane compressor is permanently mounted to the main pipe at the pre-action trim. You can also get pipe-in/pipe-out premanufactured cabinets with all the trim piped within.

'Trim' being the alarm valve, check valve, indicating valve, flow switch, solenoid, pressure switch etc.

Corrosion can be nasty of the pipework isn't treated and dried properly between activation, and you could get leaks. Double is preferred in critical, pharma and the like for this reason, but some authorities don't like the delay you get between the detector/head going off and water getting to the head.

You need to locate the riser and trim close to the protected space.